


Puberty Brings Changes

by Mochi_chan



Category: Hunter X Hunter
Genre: Aged-Up Character(s), Gon is still pretty oblivious, Killua gets even more awkward after puberty, M/M, Nosebleed, other characters get mentioned in passing
Language: English
Status: Completed
Published: 2015-08-08
Updated: 2016-08-19
Packaged: 2018-04-13 13:26:48
Rating: General Audiences
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 2
Words: 3,233
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/4523772
Author URL: https://archiveofourown.org/users/Mochi_chan/pseuds/Mochi_chan
Summary: <blockquote class="userstuff">
              <p>Puberty was supposed to be a time of growth and development and that's exactly what it was for Gon and Killua. But what Killua didn't know was that the growth and development applied in more than just a physical sense, it also applied to his feelings for his best friend.</p>
            </blockquote>





	1. Chapter 1

**Author's Note:**

> I have a serious soft spot for aged up Killua and Gon and I love all the different possibilities of what they would look like.

If there was one thing that Gon and Killua were excited for (aside from meeting Ging), it was growing up and becoming adults. Gon was constantly told by Mito that he would grow up to be tall, strong, and handsome; like his father. He told Killua this, the ex-assassin at first wasn't eager to grow up, since his family members weren't the most attractive people in the world. But, after hearing Gon's motivational words of, "You'll definitely be cool when you're older, Killua!" made the white-haired boy actually excited about the future. Time passed and the two boys were now seventeen and young men; and puberty treated them kindly, but at the same time, not kindly.

Killua's Zoldyck genes kicked in soon after his fifteenth birthday, shooting up in height, now standing at 5'10''; Gon on the other hand wasn't as lucky. The slightly older boy was always tall for his age, so when his growth spurt came, he thought he'd be around Killua's height; however, Gon learned the reality that he was actually meant to be short, standing at only 5'4''. And to make matters worse, Killua was _still_ growing. However, Gon was lucky when it came to hair, somewhere along the way, his spikes grew out and flattened, falling into a neater look that reminded Killua of his hair when he was young. Killua's hair grew out as well, but outwards rather than down like Gon's, making his already messy hair akin to a bush.

Their faces took on more mature appearances somewhat, Killua's eyes slanted and shrunk a bit while Gon's stayed large and expressive, their faces thinned out, losing the leftover baby fat that remained until their adolescence. Gon's face still held the "young boy," cute kind of look, while Killua's face was a bit more "manly"; if they worked as hosts, Gon would be the "little brother type" and Killua would be the "cool type" as they were told by Leorio. Speaking of which, the two ad become quite popular with women lately, everywhere they went, girls would talk to them and try to get them to accept a date offer. It was flattering at first, but it quickly got annoying, as the two couldn't even go to the gym and train without having girls flirting with them.

But girls weren't the only issue, due to Gon's young and cute look, he attracted men as well, men their age and men Leorio's age would give Gon their best smiles, lines, and gestures in an attempt to have fun with him, only to be thwarted by Gon's naivety and Killua's death glares. Killua had some men flirt with him, but that wasn't even close to one-percent of what Gon had to deal with, Gon was just too cute, anyone, man or woman, would want to be able to say "he's mine" and Killua knew that all too well; as he has been in love with Gon since they were twelve.

Yes, Killua had come to acknowledge and accept the fact that his feelings towards Gon were more than just being best friends, he had always known he loved Gon as a friend, but it took him until his hormones started acting up to realize he loved Gon romantically. He realized it at random intervals and instances, and whether he noticed them automatically still remains unknown to Killua; but once he thought about them all together, the conclusion was clear.

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Clue 1: Sharing a bed

Fifteen-year-olds Gon and Killua checked into a hotel rather late, it was nearing two in the morning and both were exhausted from walking all day and training. Due to short notice, they got a room with only one bed, at first it was no big deal as the two have been sharing beds for the past three years. Gon crawled in the twin-sized bed first and then Killua soon after, due to their increasing sizes, it wasn't as spacious as before; Killua took up most of the room on the mattress, so Gon placed his head on his friend's chest and wiggled closer in an attempt to be in a more comfortable position. Killua's face burned intensely and his usual snow white skin turned red.

"Killua, you okay?" Gon asked, peering up at the other, Killua didn't answer, he simply moved Gon's head onto the pillow and left the bed, "Killua?" Gon called, sitting up. "I'll sleep on the couch." Gon only stared at him and the two fell asleep soon after; the two haven't shared a bed since then.

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Clue 2: Bathing together

"Killua, come on, bath time!" Gon called from the bathroom, fourteen-year-old Killua got up from where he was, quickly stripped in the changing area of the hotel bathroom, and entered the bathing area. Deep blue eyes quickly found the body of Gon, who was currently sitting on a bath stool, shampooing his hair, Gon turned his head and saw his friend and offered him his trademark warm smile, "There you are, hey, you think you can wash my back?" he asked.

The ex-assassin felt his heart beating wildly in his chest, he had seen Gon naked plenty of times, but for some reason, this time was different. "I'm bathing later." Killua announced and left the bathroom, leaving a very confused Gon.

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Clue 3: Jealousy

"You from around here?" the older boy asked, Gon shook his head, "So, a tourist, want me to show you around?" Killua glared daggers at the stranger, the two young Hunters were at a restaurant and their freaking waiter was flirting with Gon! "Thanks, but we're gonna be leaving after we get something to eat." Gon said, "That's right, baka, now stop drooling over him!" Killua yelled in thought, the waiter frowned, "Aw, come on, don't be like that, I'm sure you can spare an hour or two." he whined.

Killua grounded his teeth together, it was _really_ difficult not to just stab the waiter with his claws and shock him with his aura, "Hey!" Killua spoke, getting the waiter's attention, "You gonna take our orders or what?" the waiter glared at Killua, presumably from interrupting his (sad, in Killua's opinion) attempt at trying to pick up Gon. "Right, terribly sorry, what can I get you two?"

The waiter managed to take their orders without throwing out flirtatious remarks at Gon, "Your order will be right out, and I'm sad you can't stay to get a tour, Gon-kun. I'll leave you with this." the waiter said, and he leaned down and pressed a kiss to Gon's cheek, making the petite boy blush and rub the spot with his hand. Every hair on Killua's head stood up in shock, "BASTARD!!!" he screamed in his mind; he was so overcome with anger, that he accidentally shot out electricity and caused the restaurant to lose power.

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Clue 4: Thoughts

Killua and Gon had been out training in the forest while visiting Whale Island and as the two were heading back to Gon's home, they got caught in a sudden storm. Seeking shelter, the two teens took cover under a large tree, "This storm came out of nowhere." Killua said, "Not really, I smelt it earlier, but I didn't know when it was coming." Gon replied, "Then why didn't you say something before!", "But I didn't know when it was coming." Killua only sighed and looked onwards at the rain. As time went by, Killua would steal occasional glances at Gon and couldn't help noticing some things, "Gon's lips look really soft." he thought.

Not even half a moment later, Killua realized what he just thought and blushed, "What the hell, Killua, why'd you go and think that?!" he asked himself, taking another glance at Gon subconsciously, "Like really, why am I just suddenly thinking that for?" Gon looked over and noticed Killua staring at him, "Hm? Killua, what's wrong? Is there something on my face?" he questioned, bringing his hands to his face and wiping all the skin his fingers could reach. "Nothing's wrong and nothing's there." Killua said, Gon brought his hands away and smiled, "That's good." Killua looked away, "Stop being so cute." he grumbled.

"Hey Killua, the rain's calmed down a bit, let's head back." Gon said, standing up, Killua followed suit and the two began walking again, "I feel like Hisoka..." Killua muttered; after that point, Killua knew he loved Gon.

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It initially came as a shock to Killua, but after he thought about it, he came to the conclusion that he couldn't imagine anyone in Gon's place and that Gon was the only one for him. There was only two issues in the way from the two young Hunters from being together; one, Killua wasn't sure Gon felt the same and two, Killua lacked enough self-confidence to confess his feelings. The ex-assassin fought with himself tooth and nail just to consider the thought of saying "I love you" to Gon plausible, but for him to actually gain the courage to say those words would be an internal war in his brain. All Killua could do was huff a sigh and hope one day he'd be able to tell Gon how he feels.

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While Killua was going through his mental turmoil, Gon was having similar issues; while Gon is naive, he isn't (entirely) stupid. He noticed all the slight changes in Killua's behavior, and he noticed the changes in routine immediately; such as no longer sleeping and bathing together and Gon can't help but wander what happened to Killua, he really misses how things used to be. "Maybe he doesn't like me anymore." Gon thought, he then shook his head rapidly, "No way, this is Killua here, he would never, he's always gonna be my best friend." But even as he tried to convince himself this, Gon couldn't help feeling that Killua was slipping away from him; and that scared him.

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"Hey Killua, I'm getting in the bath, let's go!" Gon called from the bathroom, Killua's face lit up, "Uh... I'm good, I'll go in later." he replied. Gon pouted, he left the bathroom and headed to the couch Killua was seated on, and grabbed his friend's wrist, "Come on, Killua, you smell worse than I do. If you bathe now, we'll both be clean and we can get back to training faster." he insisted, Killua looked up at the smaller and his cheeks illuminated to a vibrant pink, finally seeing that Gon was only clad in a towel. "G-GON?!" Killua shrieked, wrenching his wrist out of Gon's grip as if the contact was burning him.

Gon frowned and his eyes saddened, "What's wrong?", "Y-You're _naked_!" Killua exclaimed, face darkening, "It's not like you've never seen me naked." Gon said and Killua darkened further, "Yeah, but it's... _Different_ now!" Gon couldn't help glaring at his friend, "How? How is anything different? I'm still me and you're still you." he said, "It just is, Gon." Killua explained (or lack thereof).

"Do you not like me anymore?" Killua's face instantly lost the color it had attained and he looked at Gon with unbridled disbelief, "...What?", "Do you not like me anymore? Am I no longer your friend?" amber eyes filling with sadness and Killua thought Gon was on the verge of breaking down. The white-haired teen lifted his hands and left them suspended in air, as if wanting to grasp Gon, but couldn't bring himself to do it, "Gon, where did that come from? What does me not wanting to take a bath with you make you think you aren't my friend?", "I may be dumb, but I'm not stupid, Killua. We used to always take baths together, but then you suddenly just stopped. We also used to share a bed, but now you always ask for rooms with two beds. Killua, it's like you don't want to be anywhere near me."

Killua frowned in guilt, he was so concerned with his feelings and insecurities that he was completely ignorant to the fact that he was causing Gon insecurities, "Gon, I'm sorry. I'm so sorry." he said, as if forgetting that his best friend was naked, Killua wrapped his arms around Gon and pulled him into his chest, Gon blinked, "Killua?" Said young man took in a deep breath before talking, "Gon, the reason for me doing all of that wasn't because of me not liking you or you not being my friend, I was scared."

Gon looked up at his friend in surprise, "What do you mean?" Killua ran a hand through his hair, "I mean I was afraid of doing something to you.", "You mean like hurt me?" Gon asked, Killua shook his head, "No, Gon. You know how you thought I didn't like you, it's the opposite, I do like you. I _love_ you, and before you say 'I love you, too' you need to know what I mean. The love I feel for you is different from the love you feel to Mito-san; I want to hold you, kiss you, make you mine." Gon looked at the other in bewilderment, "Killua...", "And I don't want to share you with anyone, I want to be the one most important to you." Killua added.

"Killua wait..." Gon muttered, "I was afraid of doing something you wouldn't like, I didn't want to ruin anything." Killua continued, completely drowned out in thought, "Killua!" Gon exclaimed, "Huh?", "Two things, one, I do love you that way." Killua's heart skipped a beat, "R-really? Serious?" he questioned, Gon nodded his head.

The ex-assassin was overcome with relief and excitement that he couldn't help himself from cutting off the second part of Gon's statement and seizing the smaller around the waist and claimed the black-haired boy's lips. This was Killua's first kiss and it was definitely worth the wait, Gon's lips were even softer than he thought and he tasted sweeter than the best chocolate Killua ever had. Their height difference made things complicated, Killua was bent at an almost forty-five degree angle while Gon was standing on his toes and it was not the most comfortable position to be in; so Killua just lifted Gon up to his height and supported him as they continued to have their lips pressed together.

After a few more moments, the two finally broke apart, faces flushed, and staring into the other's eyes, Killua set Gon back down, but the two remained in a slight embrace. "Sorry, but I _really_ needed to do that." Killua said, Gon giggled, "It's okay.", "So what was the other thing you wanted to tell me?"

"Oh, my towel fell while you were hugging me and talking." Killua's face took on the resemblance of a tomato as he looked to the floor, finding the small white cotton towel left undone and then Killua couldn't help his deep blue eyes from locking onto the completely visible, soft-looking skin of Gon's legs.

 _Splurt_!

"Killua!" Gon cried to his best friend and now boyfriend, who has just passed out from a severe nosebleed. Yeah, puberty really does change people.


	2. Part 2

**Summary for the Chapter:**

> After recovering from his little mishap, Killua and Gon further explore the changes puberty brings.

**Notes for the Chapter:**

> Request from wow.ie

"Has the bleeding stopped yet?" Gon asked, now clothed and holding a box of tissues.

"Yeah, I think I'm good." Killua replied, taking a tissue and blowing his nose, ridding his nostrils of any lingering blood.

Gon smiled in relief, "That's good, I don't know why it started bleeding all crazy like that."

Killua felt the weight of Gon's obliviousness fall on his head, "Is he serious?!"

"Don't worry about it..." the taller mumbled, feeling a blush creep up, recalling the events that happened only a few minutes prior.

The onyx-haired boy cocked a brow, "Huh, but what if it starts bleeding again? We need to figure out why it happened." he insisted.

Killua flushed at the statement, "I-I know what caused it, it wasn't like it was a freak accident." the young man immediately regretted his words; he didn't mean to say it, it moreso just slipped out.

Sure enough, to Killua's groaned anticipation, Gon's curious nature got the best of him, "Wait, you do know? What was it, tell me!" he demanded, pressing up against his best friend in excitement.

"Gon, calm down, get off me!" Killua cried, his dove skin illuminating to the complexion of a cherry.

"But _Killua_ , what caused it?" Gon pleaded, stretching out the other's name in impatience.

Killua fumed before finally exploding, "Ughhhh, Gon, _you_ caused it!"

Gon cocked his head to a side, Killua mentally noting how adorable he looked, "Huh, but it's not like I punched you or anything."

The white-haired young man sighed, "I meant you looked really sexy."

The other flushed at the statement, "Sexy? Me? But, Killua is the sexy one."

Killua's milky cheeks flamed t Gon's bluntness, "And where did you learn to sweet-talk?"

"Leorio, he told me it'd come in handy with you." Gon explained, grinning happily.

Killua felt a nerve pulse in his head in irritation, "Dirty old man," he thought, "I hope that's all he taught you." he said aloud.

Gon nodded his head before leaning over and pecking his boyfriend on the nose, "Nope, Killua can teach me the rest."

Killua flushed at the implications, "Shit, those women _really did_ teach him stuff on those 'dates,' didn't they?" he said internally.

Not one to be outdone, Killua gave his best attempt at a frisky smirk, Gon's cheeks coloring ever-so-slightly, "Well, you interested in learning?"

"Sure."

The albino flushed slightly at his eagerness, but recovered quickly; as it is typical Gon, "Alright, lesson one, kissing." he said.

With that, Killua leaned in and placed his lips against Gon's, who instantaneously pressed back. Pursed lips gently applied pressure to the other, the occasional bottom lip slipping into the other's mouth.

Killua snuck his tongue out and lapped at Gon's mouth, the smaller let out a squeak of surprise. The taller smirked in satisfaction before feeling the sensation on his own lips. They opened their caverns fully, wet muscles meeting at the joining; circling and twisting, rolling and pressing.

Gon's fingers found their way into wild tresses as Killua's arms wound around the other's slim waist, pulling Gon onto his lap. Fingers clasped at Killua's scalp, the taller releasing a groan at nails pleasantly breaching skin.

Killua's hand snuck its way into the back of Gon's jacket and shirt, rubbing up and down the soft skin and sculpted muscles of the young man's back. Gon shivered at Killua's chilly hand on his warm back, but it was oddly enjoyable. The hand maneuvered to the smaller's front, fingers tracing the lines of Gon's abdomen.

" _Killua..._ " Gon breathed huskily, speaking around said boy's tongue.

Killua's face flushed, the tone of Gon's voice just then; the taller had never heard anything as seductive as that.

His adventurous hand journeyed higher, than he had realized, fingers brushing a nub, forcing Gon to pull away from the kiss.

" _Ah!_ " the smaller moaned, face illuminated.

Killua's ears rang, what had he done? He moved his fingers again, Gon quaking in response. Cerulean eyes looked to the other's chest; though obstructed by clothing, Killua knew exactly what he was touching.

Were Gon's nipples that sensitive? What would happened if Killua were to lick them?

Images rushed into Killua's brain, blood came soon after.

_Splurt_

"Killua, not again! Are you okay!?" Gon cried as blood spilled from Killua's nose once again.

**Notes for the Chapter:**

> I actually haven't written a Hunter X Hunter fic in like, two years, so it was a lot of fun to write about one of my all time favorite ships again.


End file.
